Method of calculating distance-correction data, range-finding device, and mobile object

Abstract

A method of calculating distance-correction data performed by a range-finding device includes: emitting light to a calibration target at a specified distance from a range-finding device and receiving light reflected from the calibration target that has been irradiated with the emitted light, with an optical-transmission member between the range-finding device and the calibration target, to obtain an actual-measured distance from the range-finding device to the calibration target; and calculating distance-correction data using actual-measurement error data between the specified distance and the actual measured distance to the calibration target, the distance-correction data being used to correct a distance from the range-finding device to a target object measured by emitting light to the target object and receiving light reflected from the target object that has been irradiated with the emitted light, with the optical-transmission member between the range-finding device and the target object.

What is claimed is: 
     
         1 . A method of calculating distance-correction data performed by a range-finding device, the method comprising:
 emitting light to a calibration target at a specified distance from a range-finding device and receiving light reflected from the calibration target that has been irradiated with the emitted light, with an optical-transmission member between the range-finding device and the calibration target, to obtain an actual-measured distance from the range-finding device to the calibration target; and   calculating distance-correction data using actual-measurement error data between the specified distance and the actual measured distance, the distance-correction data being used to correct a distance from the range-finding device to a target object measured by emitting light to the target object and receiving light reflected from the target object that has been irradiated with the emitted light, with the optical-transmission member between the range-finding device and the target object.   
     
     
         2 . The method according to  claim 1 ,
 wherein the specified distance includes a distance for which an error in the actual-measured distance becomes approximately maximum without correction with the distance-correction data.   
     
     
         3 . The method according to  claim 1 , further comprising obtaining at least one of measurement-error data for a distance from the range-finding device to the target object measured without the optical-transmission member between the range-finding device and the target object; and another distance-correction data obtained from the measurement-error data,
 wherein in the calculating, the distance-correction data is calculated using the actual-measurement error data and one of the measurement-error data and said another distance-correction data.   
     
     
         4 . The method according to  claim 1 ,
 wherein in the emitting, the specified distance includes at least two different specified distances, and   wherein in the calculating, the distance-correction data is calculated using the actual-measurement error data obtained from the at least two specified distances and the actual-measured distances at the at least two specified distances.   
     
     
         5 . The method according to  claim 4 ,
 wherein the emitting includes emitting light, whose intensity periodically changes, to the target object and obtaining a distance from the range-finding device to the target object using a difference in phase between the emitted light and the light reflected from the target object, and   wherein the at least two specified distances include two distances at an interval of n/2 of a cycle of the emitted light where n is a natural number.   
     
     
         6 . The method according to  claim 4 ,
 wherein the actual-measurement error data includes a mean value of errors between the at least two specified distances and the actual-measured distances.   
     
     
         7 . The method according to  claim 4 ,
 wherein the actual-measurement error data includes a mean value of absolute values of differences in errors between the at least two specified distances and the actual-measured distances.   
     
     
         8 . The method according to  claim 4 ,
 wherein the actual-measurement error data includes linear approximation error data including linearly-approximated errors between the at least two specified distances and the actual-measured distances.   
     
     
         9 . The method according to  claim 4 ,
 wherein the actual-measurement error data includes curve approximation error data including curve-approximated errors between the at least two specified distances and the actual-measured distances.   
     
     
         10 . The method according to  claim 9 ,
 wherein the curve approximation error data includes the errors that have undergone sin curve approximation.   
     
     
         11 . The method according to  claim 9 ,
 wherein the curve approximation error data includes a phase that has been corrected according to a change in speed of each of the emitted light and the reflected light, which are passing through the optical-transmission member.   
     
     
         12 . A range-finding device comprising:
 an optical-transmission member between a laser rangefinder and a target object;   the laser rangefinder configured to:   emit light to the target object and receive light reflected from the target object that has been irradiated with the emitted light to measure a distance to the target object; and   emit light to a calibration target at a specified distance from the laser rangefinder and receive light reflected from the calibration target that has been irradiated with the emitted light, with the optical-transmission member between the laser rangefinder and the calibration target, to obtain an actual-measured distance to the calibration target; and   circuitry configured to correct the measured distance to the target object using distance-correction data based on actual-measurement error data between the specified distance and the actual-measured distance.   
     
     
         13 . A range-finding device comprising:
 a laser rangefinder configured to:   emit light, whose intensity periodically changes, to a target object and receive light reflected from the target object that has been irradiated with the emitted light to measure a distance to the target object using a difference in phase between the emitted light and the light reflected from the target object; and   emit light to a calibration target at at least two different specified distances from the laser rangefinder and receive light reflected from the calibration target that has been irradiated with the emitted light, to obtain actual-measured distances to the calibration target; and   circuitry configured to correct the measured distance to the target object using distance-correction data based on actual-measurement error data between the specified distances and the actual-measured distances,   wherein the specified distances include two distances at an interval of n/2 of a cycle of the emitted light where n is a natural number.   
     
     
         14 . A mobile object comprising the range-finding device according to  claim 12 . 
     
     
         15 . The mobile object according to  claim 14 ,
 wherein the mobile object includes a cargo handling vehicle, and   wherein the range-finding device is mounted outside the cargo handling vehicle.